In the quest to identify the key sources of subjective well-being, self-determination theory (SDT) has proposed that three basic psychological needs—autonomy, competence, and relatedness—are fundamental to well-being across cultures. To understand their influence on well-being, we analyzed data from European Social Survey on 27 European countries ( n = 48,550) using structural equation modeling with alignment invariance that allowed us to get comparable indicators across the countries. Both across Europe, and within each of the 27 countries, SDT’s basic psychological needs—both when examined alone and when examined together—were strongly related to key indicators of well-being (happiness, life satisfaction, and meaning in life) and a key indicator of ill-being (symptoms of depression), even controlling for demographic factors and socio-economic position. Moreover, basic needs substantially and sometimes fully mediated the effects of socio-economic position on well-being, underscoring their status as crucial to human well-being.